The present invention relates to a gas turbine engine augmentor, and more particularly to an augmentor segment which reduces screech.
Augmentors, or “afterburners” increase the thrust of a gas turbine engine. Additional thrust is produced within an augmentor when oxygen contained within the core gas flow of the engine is mixed with fuel and burned. In some instances, additional thrust is produced by mixing and burning fuel with cooling or bypass air entering the augmentor through the inner liner of the augmentor shell as well.
One type of augmentor includes radially oriented vanes, which are circumferentially disposed around a central tail cone. The vanes include a plurality of fuel distribution apertures positioned on both sides of a line of high-pressure air apertures. The fuel distribution apertures provide fuel distribution and the line of high-pressure air apertures collectively provide pneumatic bluff bodies analogous to prior art mechanical flame holders.
Screech is a term known in the art as high-frequency pressure oscillations induced by intense combustion, which, under certain conditions, are generated in the augmentor. Uncontrolled screech reduces the high-cycle fatigue life of the augmentor due to primarily three modes of screech-induced vibration including radial, circumferential, axial, and combinations thereof.
Gas turbine engine augmentors typically include cooling liners which provide for shielding the structural augmentor casing from hot augmentor combustion gases, for providing cooling air to an exhaust nozzle disposed at the downstream end of the augmentor and for providing screech suppression. Augmentor combustion efficiency is directly proportional to the amount of available discharge gases utilized in the combustion process. Any quantity of engine discharge gas that is utilized for cooling and screech suppression and not used in the augmentor combustion process decreases augmentor thrust capability and efficiency.
Augmentors are relatively long structures when compared to overall engine size and must accommodate relatively high combustion gas temperatures. Conversely, as engine packaging constraints are reduced to minimize thermal and radar signatures, less space is available for the augmentor cooling and screech suppression systems.
Accordingly, it is desirable to provide a gas turbine engine augmentor that minimizes screech without substantially affecting augmentor performance.